<!DOCTYPE html>
<html>
<body>

<table id="theTable" border="1">
  <thead id="thead">
    <tr><th>Header</th></tr>
  </thead>
  <tfoot id="tfoot"><tr><th>Footer</th></tr></tfoot>
  <tbody><tr><td id="body">BODY</td></tr></tbody>
</table>

<script>
var style = document.getElementById('tfoot').style;
style.display = "none";
document.body.offsetWidth;
style.display = "table-footer-group";
document.body.offsetWidth;
style.display = "none";
</script>

</body>
</html>
